Yahya bin Sa'id reports from his father that al-Rabi' bin Khuthaym (may Allah have mercy on him) wrote his will: 'Bismillahir-Rahmanir-Rahim' (In the name of Allah, the Most Gracious, the Most Merciful). This is the will of al-Rabi' bin Khuthaym, and I make Allah a witness over it, and He suffices as a witness, and He is the One who rewards His righteous servants. I am pleased with Allah as Lord, with Islam as religion, and with Muhammad (peace and blessings be upon him) as Prophet. I command myself and whoever obeys me that we worship Allah among the worshippers, praise Him among those who praise, and be sincere well-wishers to all the Muslims.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الوصايا / 12685